Apollo Lunar Module
In July 1962, eleven firms were invited to submit proposals for the Lunar Excursion Module. Nine companies responded in September with a 60-page limited technical proposal answering twenty questions from NASA. Grumman was awarded the contract officially on the 7th of November 1962. The initial design looked like a smaller version of the Apollo command and service module with folding legs. A second design invoked the idea of a helicopter cockpit with large curved windows. This configuration gave rise to informal references as "the bug". As the program continued, there were numerous redesigns to save weight and improve safety. First to go were the heavy cockpit windows and the seats. Astronauts would stand while flying the LEM, supported by a cable and pulley system. Smaller triangular windows gave them sufficient visibility of the landing site. Later, the redundant forward docking port was removed. The configuration was frozen in April 1963 when ascent and descent engine designs were decided. In March 1965, fuel cells built by Pratt and Whitney were discarded in favor of an all-battery design. The name changed to Lunar Module in June 1966 eliminating the word excursion.
LM-1 was originally planned for launch in April 1967 but faced delays until the 22nd of January 1968 as Apollo 5. Development problems had been underestimated causing a ten-month delay in its first uncrewed flight. LM-3 became the first crewed LM again delayed until Apollo 9 on the 3rd of March 1969. NASA contracted Bell Aerosystems in 1964 to build the Lunar Landing Research Vehicle. This vehicle used a gimbal-mounted vertical jet engine to counter five-sixths of its weight. Successful testing of two LLRV prototypes led in 1966 to three production Lunar Landing Training Vehicles. These aircraft proved fairly dangerous to fly as three of the five were destroyed in crashes. Neil Armstrong survived one such crash using a rocket-powered ejection seat. Gus Grissom said in 1963 that pilots making this first moon landing should be highly experienced helicopter pilots. The program cost $2.29 billion nominally which adjusted to $21.65 billion in 2016 dollars. Despite these setbacks the LM became the most reliable component of the Apollo-Saturn space vehicle.
At launch the Lunar Module sat directly beneath the command and service module inside the Spacecraft-to-LM adapter attached to the S-IVB third stage. Soon after trans-lunar injection the SLA opened and the CSM turned around to dock with the Lunar Module. After achieving lunar parking orbit the commander and LM pilot entered and powered up the LM. They unfolded and locked its landing legs before separating from the CSM. A 30-second descent orbit insertion burn reduced speed and dropped the LM's perilune to within about 50,000 feet of the surface. As the craft approached perilune the descent engine started again to begin powered descent. During braking the LM descended to about 50,000 feet then down to about 4,000 feet. In final approach the vehicle pitched over to a near-vertical position allowing crew to look forward and down. Manual control was enabled for the commander who had enough propellant to hover for up to two minutes. One or more of three probes extending from footpads on the legs touched the surface activating the contact indicator light. On touchdown the probes would be bent as much as 180 degrees or even break off.
The first crewed lunar landing occurred on the 20th of July 1969 in the Apollo 11 LM-5 Eagle. Four days later the Apollo 11 crew splashed down completing President John F. Kennedy's goal. This was followed by landings by Apollo 12 and Apollo 14. In April 1970 the Apollo 13 LM-7 Aquarius saved lives after an oxygen tank rupture disabled the CSM. Aquarius served as a lifeboat for four days supporting three astronauts when designed for only two. The systems stretched to support three astronauts for 90 hours without pressurization cycles. Six landed descent stages remain at their landing sites while corresponding ascent stages crashed into the Moon following use. One ascent stage from Apollo 10 named Snoopy was discarded in heliocentric orbit. The other three LMs were destroyed during controlled re-entry in Earth's atmosphere. The four stages of Apollo 5 and Apollo 9 each re-entered separately while Apollo 13's Aquarius re-entered as a unit.
The ascent stage contained the crew cabin with instrument panels and flight controls. It held its own ascent propulsion system engine and two hypergolic propellant tanks for return to lunar orbit. A reaction control system consisted of sixteen hypergolic thrusters mounted in four quads. Internal equipment included environmental control systems and very high frequency communications systems. Electrical storage batteries stored amounts sufficient for a 48-hour stay initially extended to 75 hours for later missions. During rest periods crew slept on hammocks slung across the cabin. The descent stage primary job supported powered landings and surface extravehicular activity. Its octagonal shape was supported by four folding landing gear legs containing a throttleable Descent Propulsion System engine. Almost all external surfaces except top platform ladder descent engine and heat shield were covered in amber dark reddish amber black silver and yellow aluminized Kapton foil blankets. Equipment for exploration carried in modular equipment stowage assembly included television cameras and sample collection boxes. Extended Lunar Modules used on final three J-class missions had increased descent engine thrust and enlarged propellant tanks.
When ready to leave the Moon the LM's ascent engine fired leaving the descent stage on the surface. After course correction burns the LM rendezvoused with the CSM to transfer crew and rock samples. The Apollo 10 ascent stage engine was fired until fuel ran out sending it past the Moon into heliocentric orbit. All subsequent ascent stages except Apollo 13 were intentionally steered into the Moon to obtain readings from seismometers placed on the surface. Proposed derivatives included an orbital solar telescope constructed from surplus LMs called the Apollo Telescope Mount. This idea transferred to Skylab where only the octagonal shape remained associated with the original design. Another proposal known as the LM Truck intended to deliver up to 48,000 pounds of payload to the Moon for uncrewed landings. Unused LMs like LM-13 stand at museums including Cradle of Aviation Museum and Kennedy Space Center. Films such as First Man and Fly Me to the Moon depict these spacecraft while miniseries From the Earth to the Moon dramatized their development.
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Common questions
When was the Lunar Module contract awarded to Grumman?
Grumman received the official contract for the Lunar Excursion Module on the 7th of November 1962. This decision followed a proposal process where eleven firms were invited and nine companies submitted technical proposals in September 1962.
How did the design of the Apollo Lunar Module change from its initial concept?
The initial design featured folding legs and large curved windows resembling a helicopter cockpit before being renamed the bug configuration. Redesigns removed heavy cockpit windows and seats to allow astronauts to stand while flying, replacing them with smaller triangular windows and a cable pulley system for support.
What happened to the ascent stages of the Apollo Lunar Modules after missions ended?
Six landed descent stages remain at their lunar landing sites while corresponding ascent stages crashed into the Moon following use. One ascent stage from Apollo 10 named Snoopy was discarded in heliocentric orbit and three other LMs were destroyed during controlled re-entry in Earth's atmosphere.
Which Apollo mission used the Aquarius Lunar Module as a lifeboat?
The Apollo 13 LM-7 Aquarius saved lives after an oxygen tank rupture disabled the Command Service Module in April 1970. The spacecraft served as a lifeboat for four days supporting three astronauts when it was designed for only two crew members.
When did the name change from Lunar Excursion Module to Lunar Module occur?
The name changed to Lunar Module in June 1966 eliminating the word excursion from its title. This renaming followed the decision to freeze the configuration in April 1963 when ascent and descent engine designs were finalized.